Toyoguchi was born on born January 2, 1978 in Machida, Tokyo, Japan. In elementary school until high school, she was very interested in anime such as Dragonball. She became a fan of Tōru Furuya, the voice actor for Yamcha. In her second year of junior high school, she started to think it might be interesting to be a voice actor.

She became active in voice acting in 1998, when she was twenty years old. It was that year when she did the voice of Alice in Alice SOS. She was also Aqua and Paine in Kingdom Hearts.

Also very recently, she was Elena in Final Fantasy VII: Advent Children, and Klan Klang in Macross Frontier. She was also two characters in Danganronpa 3: The End of Hope's Peak High School: Despair Arc, is she is Tomoko Higashikata in JoJo's Bizarre Adventure: Diamond Is Unbreakable. She is Pyrrha Nikos in RWBY for the Japanese dub.

In 2016, Anime-Now.com named her a Top Five Voice Actor of that year, and they said that "her energy and emotions make the characters who they are."